ChileanJAR

The biology, morphology and population dynamicsof the ground pearI of grapes, a root inhabitmg scale insect Margarodes vitis (Phil.), was studied under: laboratory and field conditions from September 1966 to March 1969. The study was condueted in the University of Chile, Agricultural Experiment Station at Maipú.
Soil samples were collected periodically from three infested vineyards in the provinces of Santiago and O'Higgins. From March to October, only cyst form containing first to third nympihal stages were found feeding on the rbots or scattered throughout the soil profile. The majority of the cysts were found in the upper 10 to 60 cm uf the soil.
Cysts were dissected to study viability of the encIosed nymphs and to determine the stage of development of immature females. Results showed that when the cysts were placed in water, 85 to 100% of those which sank are alive. Cysts containing dead nymphs as well as fully developed females floated on the surface.
Cysts containing fully developed females are scattered throughout the soil profile but 2/3 of these cysts were found in 0-50 cm depth rather 50 to 100 cm in the soil. The percentage of adult females annually emerging from these third instar cysts was not greater than 9%. Emergence occurs from late October to late December.
Reproduction occurs parthentigenetically. Average egg production is about 600 eggs per regular to large sized females. Oviposition takes place from November to early February and the larvae appear in January and February. As soon as the larva find a suitable rootlet, introduces its mouth part into the phloem tissue and starts forming the cysts. The first molt occurs in October and the next year, in November, the second molt takes place. The length of the last (third) nymphal stage is not known.